Compute f'(x) using the limit definition. f (x) = 3x − 7

The 'marginal profit' of a good or service is defined as the instantaneous rate of change of the total profit with respect to the number of units sold. You invented a new gadget and started selling it. The total profit (in dollars) from selling x gadgets is given by: P(x) = 25x + 0.0002x³. Determine the marginal profit when 150 gadgets are sold. Use the limit definition for the instantaneous rate of change as introduced in this course, and be sure to show your work in detail and clearly.

If we need to calculate the derivative of a function at a point, there are two ways we can think about doing this. For example suppose f() = x – x, and we need to determine the value of f(4). One option is to just calculate the derivative at that point by plugging the point into the limit definition, like this: f(4 + h) – f(4) ( (4 + h)² – (4 + h)) - (4² – 4) f'(4) = lim (16 + 8h + h2 -4 – h) - (16 - 4) lim 7h + h2 = lim h(7+ h) lim h = lim h→0 h lim 7+h = 7. || h h h Another option is to calculate f'(x) in terms of x, and then plug in a value for x at the end, like this: f(x + h) – f(x) (2+ h) – (x + h)) - (2² – a) (22 + 2xh + h² – z – h) – (22 – 2) lim f'(x) = lim = lim 2xh + h2 - h h(2x + h - 1) = lim h 0 h h = lim = lim h h h that is to say, f'(x) = 2x – 1, and therefore f'(4) = 2(4) – 1 = 7. Notice that we get the answer f'(4) = 7 both ways. The second approach might look somewhat more complicated at first, but it turns out to be much more efficient if we ever need to know the…

Compute f '(x) using the limit definition. f (x) = x3